TypeError: unhashable type: 'list'

[gilbert-sun]

when i run train-your-classifier.ipynb (https://github.com/shanren7/real_time_face_recognition/blob/master/train%20your%20classifier.ipynb)

code is as below

in[7]:
data=load_data(data_dir)
keys=[]
for key in data.iterkeys():
keys.append(key)
print('foler:{},image numbers：{}'.format(key,len(data[key])))

i meet a problem, " TypeError: unhashable type: 'list' "

Would you mind telling me how to solve this problem, appreciate a lot & many thanks.

BRs,
Gilbert